The present invention relates to an inductor assembly, and in particular, to an inductor assembly that is formed from a small number of components and is easily adapted to various applications for induction heat treatment of metals or other electrically conductive materials.
Metal components of an article can be heat treated and metallurgically hardened by magnetic induction. One such article is a camshaft that has multiple lobes and bearing areas disposed along the length of a cylindrical shaft. The lobes are of an eccentric shape and are oriented in varying angular directions relative to the axial length of the shaft. The bearings are cylindrically shaped. The lobes can be heat treated and metallurgically hardened by magnetic induction. The eccentric shape of the lobes complicates the design of an inductor for use in the heat treatment process. One method is to use a top and bottom clam shell type of hinged inductor that has an opening conforming to the shape of the lobe to be heat treated. The lobe is positioned in the bottom half of the clam shell inductor and the top half of the clam shell inductor is closed around it. The clam shell inductor is connected to a suitable ac power source so that ac current flowing through the inductor will create a magnetic field that penetrates the lobe and induce eddy current in the lobe. The eddy current heats the lobe and a quench is used to metallurgically harden the lobe. Further induction hardening of the lobe may require a uniform heating pattern or a contoured heating pattern that must be accomplished in differently shaped inductors. These types of coils arc used to heat the lobes only.
An object of the present invention is an inductor assembly for induction heat treatment of electrically conductive workpieces, such as the lobes of a camshaft, that is simple in design, including an inductor formed from a single piece of bar stock; no brazing of parts; no water cooling of the inductor; and minimal machining requirements. A further object of the invention is to produce an inexpensive inductor assembly that can be used in universal induction heat treatment applications.
In one aspect, the present invention is an apparatus for, and method of, inductively heat treating workpieces with an inductor assembly. In one example of the invention, the inductor assembly comprises an inductor; a pair of flux concentrators; top, bottom and side frames; and fasteners to hold the frames in place around the inductor and flux concentrators. The inductor is formed from a single piece of stock material. AC current from a suitable power supply to the inductor creates a magnetic field that inductively heats a workpiece placed in an opening in the inductor. Quench passages can be provided in one or more of the frames and the inductor to provide a path for a quench medium to the workpiece in the opening. Induction heating patterns produced by the inductor assembly can be modified by changing the flux concentrators used in the inductor assembly. These and other aspects of the invention are set forth in this specification.